[OnionSoup] Move notification.mojom into blink/public/mojom/

This CL is part of Onion Soup effort for Notification APIs, moving
notification.mojom from blink/public/platform/modules/notifications/
into blink/public/mojom/notifications/, which facilitates moving
content/common/service_worker/service_worker.mojom into
blink/public/mojom/ in future.

This CL:
  - moves notification.mojom into blink/public/mojom/notifications/.
  - moves those native types typemapped with notification.mojom mojom
    types from content/public/common into Blink common:
        content::PlatformNotificationData
     -> blink::PlatformNotificationData
        content::PlatformNotificationData::Direction
     -> blink::PlatformNotificationData::Direction
        content::NotificationResources
     -> blink::NotificationResources
  - of course, moves the corresponding struct traits from Content common
    into Blink common as well.

BUG=595685,789846

Change-Id: Id4e43f5f290ee248ee29e71cb05b62197b47c180
Reviewed-on: https://chromium-review.googlesource.com/1195114
Commit-Queue: Han Leon <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Peter Beverloo <[email protected]>
Cr-Commit-Position: refs/heads/master@{#589107}
diff --git a/chrome/browser/push_messaging/push_messaging_notification_manager.h b/chrome/browser/push_messaging/push_messaging_notification_manager.h
index dfe67f6..f682d90 100644
--- a/chrome/browser/push_messaging/push_messaging_notification_manager.h
+++ b/chrome/browser/push_messaging/push_messaging_notification_manager.h
@@ -19,10 +19,13 @@
 
 namespace content {
 struct NotificationDatabaseData;
-struct PlatformNotificationData;
 class WebContents;
 }
 
+namespace blink {
+struct PlatformNotificationData;
+}
+
 // Developers may be required to display a Web Notification in response to an
 // incoming push message in order to clarify to the user that something has
 // happened in the background. When they forget to do so, a default notification
@@ -82,14 +85,14 @@
   static void DidWriteNotificationDataIOProxy(
       const base::WeakPtr<PushMessagingNotificationManager>& ui_weak_ptr,
       const GURL& origin,
-      const content::PlatformNotificationData& notification_data,
+      const blink::PlatformNotificationData& notification_data,
       const base::Closure& message_handled_closure,
       bool success,
       const std::string& notification_id);
 
   void DidWriteNotificationData(
       const GURL& origin,
-      const content::PlatformNotificationData& notification_data,
+      const blink::PlatformNotificationData& notification_data,
       const base::Closure& message_handled_closure,
       bool success,
       const std::string& notification_id);